Kinetics and mechanistics steps to the electron transfer reaction of peroxo-bridged binuclear cobalt(III) complex of succinimide by glycine in aqueous acidic medium

Abstract

ABSTRACT. The kinetics and mechanistic steps to the electron transfer reaction of the peroxo-bridged binuclear cobalt(III) complex of succinimide [(suc)(en)₂Co(O₂)Co(en)₂(suc)²⁺] hereafter called peroxo-bridged dicobalt(III) complex ‘[Co(O₂)Co²⁺]’ by glycine have been carried out spectrophotometrically at λ = 420 nm and T = 26 ± 1 ^oC, [H⁺] = 1 x 10^-3 M and ᶙ = 0.5 M (NaCl) in aqueous acidic medium. The reaction was found to be first order with respect to [Co(O₂)Co²⁺] and [(Gly] and experimental data indicates a second-order overall. The reactions obeyed the general rate law: (d[Co(O₂)Co²⁺]/dt) = (a +b)[H⁺])[Co(O₂)Co²⁺][Gly]. Varying hydrogen ion concentration accelerated the reaction rate and shows first-order dependence while the reactions also affected by changes in the ionic strength of the reaction medium by giving a non-negative salt effect in the course of the reaction. Free radicals were not detected in the reactions. Spectroscopic investigation and Michaelis-Menten plots suggest the absence of intermediate complex formation. The experimental result obtained in this system is concluded in favor of the outer-sphere mechanism.

KEY WORDS: Cobalt(III) complex, Kinetic, Electron transfer, Spectroscopic, Mechanistic steps, Michaelis-Menten, Glycine

Bull. Chem. Soc. Ethiop. 2021, 35(2), 425-434.

DOI:  https://dx.doi.org/10.4314/bcse.v35i2.15